Safety knife



FIG. 1 is a perspective view of the safety knife;

FIG. 2 is a front view of the safety knife;

FIG. 3 is a rear view of the safety knife;

FIG. 4 is a top view of the safety knife;

FIG. 5 is a bottom view of the safety knife;

FIG. 6 is a right side view of the safety knife; and,

FIG. 7 is a left side view of the safety knife.

The broken line portions of the drawings form no part of the claimed design. 

The ornamental design for a safety knife, as shown. 